Combustion chambers for gas turbine engines

ABSTRACT

A combustion chamber for a gas turbine engine has a primary air inlet and a number of additional air nozzles at intervals along the chamber. Each of the air inlets has one or more holes in the inlet wall, so that air may be injected into the inlets or extracted therefrom. Air injection effectively reduces the inlet areas and extraction increases the inlet areas. The airflow through each inlet, or group of inlets, may thus be controlled, the arrangement being such that, irrespective of the proportion of the total airflow which enters each inlet, the resistance to airflow through the combustion chamber does not vary. The holes in the inlet walls may be tangential to create a vortex within the inlet.

United States Patent [72] lnventor Alan Joseph Gerrard Blackburn,England [21] AppLNo. 858,770

[22] Filed [45] Patented [73] Assignee Sept. 17, 1969 July 20, 1971Joseph Lucas Industries Limited [54] COMBUSTION CHAMBERS FOR GAS TURBINEENGINES 7 Claims, 4 Drawing Figs.

[52] US. Cl 60/39.65, 60/3923, 431/352 [51] lnt.Cl F02c9/14 [50] Fieldof Search 60/3965,

39.23, 39.29, 39.69; 137/13, 13.], 13.2, 81,5;415/168,115,ll6,144,108;43l/350-353; 123/119, 119 C; 261/64, 69;239/D1G. 3

[56] References Cited UNlTED STATES PATENTS 2,807,933 10/1957 Martin60/3965 2,841,182 7/1958 Scala 60/3965 3,394,543 7/1968 Slattery 60/3965FOREIGN PATENTS 738,006 10/1955 Great Britain 60/3965 PrimaryExaminer-Douglas Hart Attorney-Holman & Stern ABSTRACT: A combustionchamber for a gas turbine engine has a primary air inlet and a number ofadditional air'nozzles at intervals along the chamber. Each of the airinlets has one or more holes in the inlet wall, so that air may beinjected into the inlets or extracted therefrom. Air injectioneffectively reduces the inlet areas and extraction increases the inletareas. The airflow through each inlet, or group of inlets, may thus becontrolled, the arrangement being such that, irrespective of theproportion of the total airflow which enters each inlet, the resistanceto airflow through the combustion chamber does not vary. The holes inthe inlet walls may be tangential to create a vortex within the inlet.

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I -FTBRNEYS COMBUSTION CHAMBERS FOR GAS TURBINE ENGINES This inventionrelates to combustion chambers for gas turbine engines and hasas anobject to provide a combustion chamber in a convenient form.

A combustion chamber in accordance with the invention has a primary airinlet duct, secondary air inlet nozzles and dilution air inlet nozzles,each air entry point incorporating a fluidic airflow control devicearranged so that the proportions of the total airflow through therespective air entry points can be varied without variation of the totalresistance of the combustion chamber to airflow therethrough.

In the accompanying drawings FIG. 1 is a fragmentary section through anannular combustion chamber incorporating an example of the invention,

FIG. 2 is a fragmentary enlargement of the part ringed in FIG. 1 andFIGS. 3 and 4 show, somewhat diagrammatically, two views of a part of analternative embodiment.

The combustion chamber has an inner wall and an outer wall 11 shapedtojoin at a circular leading end in which primary air inlet ducts 12 areformed. Each primary air inlet duct has a swirler 13 which incorporatescontrol jet holes 14 through which high-pressure air can be injected.These holes 14 are arranged around the outer periphery of the swirler 13so that when compressed air is injected the effective area of theswirler is reduced fluidically to reduce the airflow through the primaryair inlet ducts. Conversely, when air is bled off through the holes 14the effective area of the swirler is increased fluidically to increasethe airflow through the primary inlet duct. 7

The walls 10, ll of the combustion chamber adjacent the inlet endthereof are formed with secondary air inlet nozzles 15 constituted byinwardly directed flanges on the walls. In association with the nozzles15 is an annular dished member 16 defining an annular air chamber 17.Drillings are formed in the flanges which open into the nozzles 15 onthe upstream sides thereof. Thus when high-pressure air is applied tothe chambers 17 jets will issue into the nozzles 15 and fluidicallyrestrict flow of air into the combustion chamber. If on the other handair is drawn from the chambers 17 the effective area of the nozzles 15will be increased so that there will be increased airflow through thenozzles 15.

Downstream of the nozzles 15 the walls 10, 11 have dilution air inletnozzles 18 similar to the nozzles 15. These nozzles 18 similarly haveassociated therewith fluidic flow control devices constituted bydrillings in the nozzle flanges opening into chambers 19 to which air issupplied to decrease the effective areas of nozzles 18 and from whichair is drawn to increase the effective area.

It will be noted that the provision of the fluidic control drillings onthe upstream side only of the nozzles has the effect of changing thedirection of the airflow through the nozzles as well as reducing theeffective cross-sectional area of the nozzles.

At engine running conditions associated with the weaker overall air/fuelratios for the combustion chamber, e.g., aircraft standoff flightconditions, the fluidic devices mentioned above are actuated to decreaseflow through the primary and secondary air nozzles to a minimum value,whilst air is drawn from the chambers 19 to increase the airflow throughnozzles 18 to a maximum value. At engine running conditions associatedwith the richer overall air/fuel ratios for the combustion chamber,e.g., aircraft takeoff conditions, the supply of compressed air to theholes 14 is stopped and air is drawn from chambers 17 so that theprimary and secondary airflows are increased. The chambers 19 arepressurized to reduce the dilution airflow. This changes the pattern ofairflow in the combustion chamber to increase the quantity of airavailable to the burners which would be situated in the centers of therespective swirlers 13. The change in direction of the secondary airflowcauses increased reverse flow of secondary air to increase the rateofintermixing of fuel and air. I

It IS to be noted that the upper half of FIG. 1 shows airflow conditionsobtaining at low throughput and the lower half shows conditions at highthroughput.

The fluidic devices used in nozzles 15 and 18 may alternatively take theform of vortex amplifiers as shown in FIGS. 3 and 4 in which there arecontrol drillings which can direct tangential jets of air into thenozzles to create swirl which will effectively reduce the area of thenozzles.

ln either case the a eas of the nozzles, the sizes of the controldrillings and the control pressures used would be chosen so that thereis no change in the overall resistance of the combustion chamber toairflow when changeover from one flow condition to the other takesplace.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

l. A combustion chamber which includes a primary air inlet duct,secondary air inlet nozzles and dilution air inlet nozzles, each airentry point incorporating a fluidic airflow control device arranged sothat the proportions of the total airflow through the respective airentry points can be varied without variation of the total resistance ofthe combustion chamber to airflow therethrough.

2. A combustion chamber as claimed in claim 1 in which the primary airinlet duct incorporates holes through which air may be injected orwithdrawn so as respectively to increase or decrease the effective areaof the duct.

3. A combustion chamber as claimed in claim 2 in which the said holesare formed in the outer periphery of the duct.

4. A combustion chamber as claimed in claim 1 in which the secondary airinlet nozzles are constituted by inwardly directed flanges on the wallsof the chamber, said flanges being formed with drillings in the upstreamsides thereof through which air may be injected or withdrawn so asrespectively to reduce or increase the effective areas of the nozzles.

5. A combustion chamber as claimed in claim 1 in which the dilution airinlet nozzles are constituted by inwardly directed flanges on the wallsof the chamber, said flanges being formed with drillings through which,in use, high-pressure air is injected tangentially into the nozzles.

6. A combustion chamber as claimed in claim 1 in which the dilution airinlet nozzles are constituted by inwardly directed flanges on the wallsof the chamber, said flanges being formed with drillings in the upstreamsides thereof through which air may be injected or withdrawn so asrespectively to reduce or increase the effective areas of the nozzles.

7. A combustion chamber as claimed in claim 1 in which the secondary airinlet nozzles are constituted by inwardly directed flanges on the wallsof the chamber, said flanges being formed with drillings through whichin use high pressure air is injected tangentially through the nozzles.

1. A combustion chamber which includes a primary air inlet duct,secondary air inlet nozzles and dilution air inlet nozzles, each airentry point incorporating a fluidic airflow control device arranged sothat the proportions of the total airflow through the respective airentry points can be varied without variation of the total resistance ofthe combustion chamber to airflow therethrough.
 2. A combustion chamberas claimed in claim 1 in which the primary air inlet duct incorporatesholes through which air may be injected or withdrawn so as respectivelyto increase or decrease the effective area of the duct.
 3. A combustionchamber as claimed in claim 2 in which the said holes are formed in theouter periphery of the duct.
 4. A combustion chamber as claimed in claim1 in which the secondary air inlet nozzles are constituted by inwardlydirected flanges on the walls of the chamber, said flanges being formedwith drillings in the upstream sides thereof through which air may beinjected or withdrawn so as respectively to reduce or increase theeffective areas of the nozzles.
 5. A combustion chamber as claimed inclaim 1 in which the dilution air inlet nozzles are constituted byinwardly directed flanges on the walls of the chamber, said flangesbeing formed with drillings through which, in use, high-pressure air isinjected tangentially into the nozzles.
 6. A combustion chamber asclaimed in claim 1 in which the dilution air inlet nozzles areconstituted by inwardly directed flanges on the walls of the chamber,said flanges being formed with drillings in the upstream sides thereofthrough which air may be injected or withdrawn so as respectively toreduce or increase the effective areas of the nozzles.
 7. A combustionchamber as claimed in claim 1 in which the secondary air inlet nozzlesare constituted by inwardly directed flanges on the walls of thechamber, said flanges being formed with drillings through which in usehigh pressure air is injected tangentially through the nozzles.